Google recently incorporated a new security measure for embedded images in the email you receive. Their system automatically caches the image and displays the cached version. This is an added safety feature for GMail users but may still pose limited exposure for spammers and marketers.
This may not eliminate spam all together but it does make it slightly less convenient for spam or marketing firms to gain your info via embedded images.
Because of this new system, Google has made the default setting of Gmail to display all images. This isn't good, but easily remedied.
Simply go to your Settings in Gmail
Then make sure you select "Ask before displaying external images". And while you're at it, enable "Always use HTTPS" in the browser setting. Save your settings.